MEG Study of Acute STX209 Effects in ASD

Recent evidence from magnetoencephalographic (MEG) studies in ASD have pointed to abnormalities (specifically, delays) in auditory evoked neuromagnetic responses (e.g. M100 - see Roberts et al., 2010, and mismatch field, MMF - see Roberts et al., 2011) as well as abnormalities in the oscillatory behavior of auditory cortex, especially in the gamma band (30-50Hz), at rest and in response to simple auditory stimuli (see Gandal et al., 2010 and Cornew et al., 2012; Edgar et al., 2013). The local circuitry underlying such evoked activity and oscillations, and synaptic transmission in general, requires an appropriate balance of excitation and inhibition, mediated by glutamate and GABA, respectively. One model of the neural oscillatory deficits in ASD suggests that impaired regulatory control by inhibitory interneurons onto pyramidal cells underlies abnormal auditory latency and oscillatory electrophysiological measures. As such, electrophysiological deficits are interpreted in terms of local circuitry abnormalities, with inferences at the molecular level of imbalances in the activity of glutamate and GABA. A candidate therapeutic for ASD has been developed - STX209, a GABA-B agonist. Since this pharmaceutical targets synaptic activity that has clear electrophysiological correlates, one goal of this proposal is to assess the responsiveness (sensitivity to change) of MEG measures to acute administration of STX209 at various doses in adolescents on the autism spectrum. The study also aims to establish the nature of the putative relationship between such electrophysiologic markers and GABA and glutamate levels using MEGAPRESS spectrally-edited magnetic resonance spectroscopy (MRS).